It is known that D-galactose is converted in vitro into D-glucose-1-phosphate by the enzyme system including galactokinase (EC 2.7.1.6) and galactose-1-phosphate transferase (EC 2.7.7.10), and utilized.
In a dysbolism wherein the enzyme system is hereditarily deficient, the D-galactose accumulated in the body is reduced by aldose reductase (EC 1.1.1.21) into galactitol which is present in body fluids such as blood, urine, etc.
It is known that galactitol, accumulated in a large quantity in the body, crystallizes in the lens and becomes one of the major factors of cataract.
For this reason, galactitol in the body fluid, such as blood and ruine, should be qualitatively and quantitatively determined for prevention and diagnosis of cataract.
The methods which are generally employed to determine galactitol are those for polyols as reported, for example, in J. S. Dixon et al., Analytical Chemistry, Vol.26, pp.1092-1093 (1954), wherein polyols are oxidized with periodate and the reaction product is developed and then subjected to colorimetry. The method determines polyol in total but does not give the levels of particular polyols. In addition, the data obtained with the methods must be compensated because reducing substances such as glucose tend to interfere the methods.
Galactitol is also determinable by gas-chromatography. Gas-chromatography of galactitol, however, has the drawback of unfavorably requiring, in addition to complicated pretreatments such as trimethylsilylation, a high experimental skill to allow fractional determination of other polyols such as D-mannitol, D-sorbitol, etc.